In a semiconductor chip, especially in a digital chip (e.g., a processor chip, a controller chip and a memory chip), more than one supply voltage is used. A high supply voltage is used for the periphery as well as for input/output components of the chips. A lower supply voltage is used for the processor or memory core supply. A core voltage having a low level allows for the use of faster thin oxide transistors, to filter some of the supply noise, and to reduce power consumption.
A chip of an integrated circuit (e.g., a semiconductor memory) comprises voltage supply pads from which the supply voltage is distributed to several areas of the chip by a power distribution network. Especially for high current consuming parts situated far away from the supply pads, undesired voltage drops may occur over the power distribution network.
If a ground connection of the power distribution network is implemented with very low resistivity, the ground level will be approximately the same over the entire power distribution network of the chip, and voltage generators spread over the chip area are providing the same local voltage levels. However, for relatively high-resistive ground connections a respective output current of a respective voltage stabilizer or its neighbors could produce a significant voltage drop on local ground nodes.
In a power distribution network voltage drops could be easily in a range of 50 millivolts (mV) in the case where external supply voltages Vext are provided in a range of, for example, 1.5 V. If the level of a control voltage for controlling a respective voltage stabilizer is not corrected with respect to any local ground, the output voltage generated by each of the local voltage stabilizers will be lower by up to 50 mV correspondingly.
Furthermore, a load current generated at an output terminal of a voltage stabilizer could change very fast between its minimum and maximum values. Therefore, in a power distribution network a load current may change in a range of 0 . . . 25 mA per each voltage stabilizer. For modern DRAM chips the number of such voltage stabilizers could be in range of 50 and overall core current consumption could be in range of 1 A.
In a power distribution network a first load voltage may be measured with a dynamical change between 1.3 V . . . 1.263 V. A second load voltage may be measured with a dynamical change range between 1.3 V . . . 1.25 V, and a far-end load voltage may be measured with a dynamical change in between 1.3 V . . . 1.225 V because of uncompensated ground drops.